Charging Voltage Cycling in Image-Forming Apparatuses for Toner Transfer
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Solution Overview
Problem
Existing image-forming apparatuses using a cleanerless method face issues with toner contamination on the charging roller, leading to increased adhesion force and difficulty in transferring toner onto the drum, resulting in defective images due to varying discharge thresholds and toner polarity changes.
Innovation Solution
An image-forming apparatus with a control unit that alternately applies charging voltages of opposite polarities to the charging member during non-image-forming operations to manage toner contamination on the charging roller, ensuring effective transfer of toner to the drum surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charging voltage higher than or equal to the discharge threshold is applied to the charging member during cleaning operation, then toner adhering to the charging roller can be transferred onto the drum surface, but the toner may be charged to a polarity opposite to the charging voltage, increasing adhesion force and making transfer difficult
Solution Approach 1:
The charging voltage is applied periodically in alternating cycles: first applying a voltage below the discharge threshold to prevent opposite polarity charging and maintain low adhesion, then applying a voltage above the discharge threshold to enable toner transfer. This periodic switching between sub-threshold and super-threshold voltages resolves the contradiction by timing the high-voltage transfer phase to occur after toner has accumulated on the drum surface, while preventing opposite polarity charging during the low-voltage maintenance phase.
Solution Approach 2:
The charging voltage parameter is dynamically changed between two distinct levels: a first voltage level below the discharge threshold that prevents opposite polarity charging and maintains low adhesion force, and a second voltage level above the discharge threshold that enables effective toner transfer. By controlling the timing and duration of each voltage level, the system optimizes both toner transfer reliability and prevents harmful opposite polarity adhesion.
2Object-generated harmful factors
If the charging voltage is kept below the discharge threshold to prevent opposite polarity charging, then toner adhesion remains manageable, but effective toner transfer to the drum surface becomes difficult
Solution Approach 1:
The system employs periodic voltage cycling where the charging voltage alternates between a sub-threshold level (for adhesion control) and a super-threshold level (for transfer effectiveness). The sub-threshold voltage is applied for extended periods to maintain low adhesion and prevent opposite polarity charging, while brief super-threshold pulses are applied at intervals to ensure complete toner transfer, thus resolving the contradiction between adhesion control and transfer effectiveness.
Solution Approach 2:
The charging voltage is preliminarily set below the discharge threshold during initial charging phases to prevent opposite polarity charging and establish controlled adhesion conditions. This preliminary low-voltage charging prepares the system for subsequent high-voltage transfer pulses, ensuring that when the high voltage is applied, toner transfer occurs efficiently without the complication of opposite polarity adhesion.
3Device complexity
If a cleanerless method is used to reduce apparatus size, then the structure is simplified and size is reduced, but remaining toner on the drum surface contaminates the charging member, causing image density variation
Solution Approach 1:
The charging member performs a self-cleaning function by utilizing the potential difference between itself and the drum surface. By applying charging voltages that create sufficient potential difference, toner adhering to the charging member is automatically transferred to the drum surface during the charging process, eliminating the need for a separate cleaner component and maintaining image quality consistency without increasing apparatus complexity.
Solution Approach 2:
The charging member is designed to perform multiple functions: it charges the drum surface for image formation and simultaneously cleans itself by transferring adhered toner to the drum surface. This multi-functionality is achieved by optimizing the charging voltage characteristics to create conditions where toner transfer occurs during normal charging operations, thereby eliminating the need for dedicated cleaning components and maintaining image quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces toner contamination on the charging roller, preventing defective images by alternately applying charging voltages to manage toner polarity and discharge, thereby maintaining image quality.
Implementation Method 1
a charging member to be in contact with a surface of the image bearing member to form a charging portion, the charging member being configured to charge the surface of the image bearing member at the charging portion
Implementation Method 2
in the non-image-forming operation, the control unit executes the following control processing: applying a first charging voltage having a first polarity with respect to a surface potential on the surface of the image bearing member to the charging member; applying a second charging voltage having a polarity opposite to the first polarity with respect to the surface potential
Data Source
AI summary
An image-forming apparatus, wherein, in a non-image-forming operation, a control unit executes the following control processing: i) not discharging electric charge between the charging member and the image bearing member and applying a first voltage having a first polarity with respect to a potential on the image bearing member to the charging member; ii) after performing the processing of i), applying a second voltage having a polarity opposite to the first polarity with respect to the potential; and iii) after performing the processing of ii), controlling a third voltage having a second polarity with respect to the potential to be applied to the charging member and controlling a fourth voltage having a polarity opposite to the second polarity with respect to the potential to be applied to the charging member, and controlling electric charge to be discharged between the charging member and the image bearing member.